Golf club head with uniform response front face

ABSTRACT

A golf club head has a face insert the effective resiliency of which varies across a striking surface on a front face of the club head. The face insert, which is disposed in a cavity formed in the club head, is supported from beneath by a substrate which is formed of one or more materials to form a low resiliency region near a central of the cavity and a high resiliency region near heel and toe regions of the cavity. By varying the resiliency of the substrate behind the face insert, the effective resiliency, which is a composite of the face insert and the substrate, may be manipulated so that the effective coefficient of restitution between the club head and a golf ball may be made uniform across the entire front face.

BACKGROUND OF THE INVENTION

This invention relates generally to golf equipment and, in particular,to golf club heads.

As is well known to golf manufacturers and many golfers, the “sweetspot” of a golf club head is the point on the front face at which a linedrawn normal to the front face passes through the center of gravity ofthe golf club head. If a golfer swings a golf club so that the club headimpacts the golf ball at the sweet spot, few if any harmonic vibrationsare excited within the golf club head and shaft system. Consequently,the maximum amount of energy from the golfer's swing is available formomentum transfer to the golf ball. Conversely, if the golfer swings thegolf club so that it impacts the golf ball away from the sweet spot, theimpact frequently excites various torsional and bending oscillations.Such a mis-hit has two deleterious consequences. The harmonicoscillations are felt as unpleasant vibrations transmitted to thegolfer's hands and the energy lost through the harmonic oscillations isnot available for momentum transfer to the golf ball thus resulting in ashorter distance of travel for the golf ball for the same swing speed.This effect is compounded by the fact that in many cases the sweet spoton the front face is at or near the point of the front face which hasthe highest compliance and therefore, the highest effective coefficientof restitution. Thus, a golf ball hit at the sweet spot will travelsubstantially further than a golf ball hit at a point on the front faceaway from the sweet spot. Accordingly, it would be advantageous toprovide a golf club head having a lower resilience toward the center ofthe club head and a higher resiliency toward heel and toe ends of theclub head so that the energy transferred to the golf ball would beuniform across the front face irrespective of where the impact occurs.

U.S. Pat. No. 5,807,190 to Krumme, et al. discloses a club head in whichthe face insert is composed of many small rods arranged in a closelypacked array. According to the Krumme patent, use of individual rodsegments to form the front face allows the properties of the front faceto vary in any pattern over the impact area, simply by varying thematerials out of which the individual rods are made. Use of multiplematerials within the array of rods could render a front face having thedesired distribution of resiliency. Such use of multiple materialswould, however, render the club hard non-conforming, for Rule 5(b) ofAppendix II of the United States Golf Association requires that thewhole of the impact area of a club head be of the same material.Accordingly, what is needed is a golf club head in which the resiliencyof the face may be varied across the front face without varying the rodmaterial.

SUMMARY OF THE INVENTION

The present invention comprises a golf club head having a face insertthe effective resiliency of which varies across a striking surface on afront face of the club head body. According to an illustrativeembodiment, the club head body has a cavity for receiving a face insert.The face insert, which is disposed in the cavity, is supported frombeneath by a substrate sandwiched between a back surface of the faceinsert and a bottom surface of the cavity. The substrate is formed ofone or more materials to provide the substrate with low resiliency neara central region of the cavity and higher resiliency near either a heelregion or a toe region of the cavity. By varying the substrate, theeffective resiliency, which is a composite of the face insert andsubstrate, may be manipulated so that the effective coefficient ofrestitution between the club head and a golf ball may be made uniformacross the entire front face.

DESCRIPTION OF THE DRAWINGS

The present invention will be better understood from a reading of thefollowing detailed description, taken in conjunction with theaccompanying drawings figures in which like references designate likeelements and, in which:

FIG. 1 is a front perspective view of a golf club head incorporatingfeatures of the present invention;

FIG. 2 is a cross-sectional view of the golf club head of FIG. 1 takenalong line 2-2; and

FIG. 3 is a cross-sectional view of an alternative embodiment of a golfclub head incorporating features of the present invention.

DESCRIPTION OF THE INVENTION

The drawing figures are intended to illustrate the general manner ofconstruction and are not necessarily to scale. In the detaileddescription and in the drawing figures, specific illustrative examplesare shown and herein described in detail. It should be understood,however, that the drawing figures and the detailed description are notintended to limit the invention to the particular form disclosed but aremerely illustrative and intended to teach one of ordinary skill how tomake and/or use the invention claimed herein and for setting forth thebest mode for carrying out the invention.

With reference to FIGS. 1 and 2, a golf club head 10, preferably a golfputter head, comprises a club head body 12 attached to a golf club shaft14. Typically, the club head body 12 is made of a suitable metal such assteel formed by an investment casting process, however, metal materialssuch as titanium, aluminum, tungsten, brass, bronze and beryllium coppermay be used to form club head body 12. Those skilled in the art willrecognize also that the club head body 12 may be made of other metallicor non-metallic materials without departing from the spirit and scope ofthe present invention. Club head body 12 has a front face 16, a rearsurface 18, a heel end 20 and a toe end 22, as well as a top rail 24 andsole 26.

As shown most clearly in FIG. 2, club head body 12 is formed with acavity 28 that extends from the front face 16 toward the rear surface 18and is defined by side wall 30 and bottom wall or surface 32. A strikingsurface 34 on the front face 16 of club head body 12 is provided by afront face insert 36 supported by a substrate 38 disposed in cavity 28.Substrate 38 is preferably composed of additional face inserts 40, 42and 44. Face insert 36 preferably comprises a plurality of individualrod elements 46. Rod elements 46 are all of substantially identicalgeometry except for their individual lengths. Accordingly, theindividual rod elements 46 are not separately described herein indetail. Rod elements 46 are packed together in an array such that eachside surface 48 is in contact with the side surface of an adjacent rodelement 46. Face insert 36 is positioned in cavity 28 such that thebottom ends 50 of the rod elements 46 are supported by the uppersurfaces 52, 54 and 56 of face inserts 40, 42 and 44. The exposed ends58 of rod elements 46 are finished flat to form the striking surface 34on the front face 16. Face insert 36 may be formed of individual rodelements of circular cross-section (not shown), but preferably comprisesa plurality of metal alloy rod elements 46 of hexagonal cross-section(as seen in FIG. 1) arranged in a close-packed array surrounded by anepoxy binder 60 that holds the rod elements 46 in place.

Face insert 40, which is positioned in a central region 62 of cavity 28is preferably made from an elastomer such as polyurethane having aresiliency of between 0.5 and 0.85. Face inserts 42 and 44 may be madeof a metal alloy, ceramic or elastomer having a resiliency greater thanthat of face insert 40. The material choices for face inserts 40, 42 and44 will vary from club head to club head depending on the location ofthe vibrational nodes and anti-nodes of the golf club head.

Where a principal node of the club head is located in the central region62 of cavity 28, little energy is lost due to the excitation of harmonicvibrations within the club head 10. Accordingly, a golf ball will travela greater distance for a given club head speed. Conversely, if a golfball is struck in a heel region 64 of cavity 28 proximal face insert 42,energy will be lost due to the excitation of harmonic vibrations in club10 and the ball will not travel as far. Similarly, if a golf ball isstruck in a toe region 66 of cavity 28 proximal face insert 44, energywill be lost due to the excitation of harmonic vibrations in club head10. The energy lost in a “toe hit” versus a “heel hit” may or may not bethe same. Therefore, in order to compensate separately for a “toe hit”or “heel hit”, the material chosen for face inserts 42 and 44 may be ofdifferent resiliencies so as to dissipate different amounts of energy.

The effective coefficient of restitution, as used herein, is the ratioof the velocity of a golf ball struck by the golf club head at variouslocations on the front face as compared to the velocity of the golf ballin a perfectly elastic collision. The apparent coefficient ofrestitution C for a golf club of mass M1 travelling at a velocity V1 andstriking a stationary golf ball of mass M2 may be described by thefollowing equation:C=(V _(2b) −V _(2c))/(V _(1c) −V _(1b))Where V_(1c) is the the club head velocity before impact, V_(1b) is theball velocity before impact, V_(2c) is the club head velocity afterimpact, and V_(2b) is the ball velocity after impact.

The effective coefficient of restitution will be a function of not onlythe composite resiliency of face insert 36 and any one of face inserts40, 42 and 44 but also the energy lost due to the aforementionedexcitation of vibrations within the club head. Since the material offace insert 36 must be the same across the entirety of striking surface34, and since the losses introduced as a result of exciting harmonicvibrations within golf club head 10 are difficult to control, theeffective coefficient of restitution can be made uniform across thestriking surface 34 most effectively by reducing the resiliency of faceinsert 40 relative to face inserts 42 and 44 so that the sum of theenergy lost due to the resiliency of the face inserts 42, 44, 46 plusthe energy lost due to the excitation of harmonic vibrations is equalacross the front face 16 of the body 12. Although the resiliency of faceinsert 36 has some effect on the overall resiliency, the overallresiliency of striking surface 34 is dominated by the resiliency ofsubstrate 38. Therefore, the overall resiliency of striking surface 34can be manipulated by altering the resiliency of substrate 38notwithstanding the presence of face insert 36. The result is that, fora given club head velocity, the golf club head will impart the sameinitial velocity to a golf ball irrespective of where on the front facethe golf ball is hit.

With reference to FIG. 3, an alternative embodiment of a golf club headincorporating features of the present invention comprises a club headbody 312 having a front face 316, a rear surface 318, a heel end 320 anda toe end 322. A cavity 328 with a side wall 330 extends from the frontface 316 toward the rear surface 318 and terminates in a bottom wall329. As with the illustrative embodiment of FIG. 2, a face insert 336 issupported by a substrate 338 composed of face inserts 340, 342 and 344.In order to provide a smoother transition from the high resiliency heeland toe regions 341, 343 proximal face inserts 342 and 344 to the lowresiliency region 345 proximal face insert 340, transition regions 346and 348 are provided in which face insert 340 is partially supported byface inserts 342 and 344, which causes the effective coefficient ofrestitution in transition regions 346 and 348 to be a composite thatincludes the resiliency of face insert 340 as well as the resiliency offace insert 342 and face insert 344.

Although certain illustrative embodiments and methods have beendisclosed herein, it will be apparent from the foregoing disclosure tothose skilled in the art that variations and modifications of suchembodiments and methods may be made without departing from the spiritand scope of the invention. For example, first face insert may be asolid insert or a veneer rather than a plurality of rod elements.Accordingly, it is intended that the invention should be limited only toextent required by the appended claims and the rules and principals ofapplicable law.

1. A golf club head comprising: a body having a front face, a rearsurface and a cavity extending from the front face toward the rearsurface, said cavity having a bottom surface; a first face insert formedof a first material, said first face insert having a front surface and aback surface, said first face insert disposed within the cavity with theback surface of said first face insert adjacent the bottom surface ofthe cavity; a second face insert formed of a second material, saidsecond face insert having a front surface and a back surface, saidsecond face insert disposed within the cavity with the back surface ofsaid second face insert adjacent the bottom surface of the cavity; and athird face insert disposed within the cavity atop said first face insertand said second face insert, said third face insert including aplurality of elongate rod elements each having a first end, a second endand a side surface, said plurality of elongate rod elements arranged ina parallel closely packed array such that the side surface of each ofsaid plurality of elongate rod elements is in contact with the sidesurface of an adjacent one of said plurality of elongate rod elements,the first ends of said plurality of elongate rod elements abutting thefront surface of one of said first face insert and said second faceinsert, and said second ends of said plurality of elongate rod elementsexposed to form a striking surface on the front face of the body.
 2. Thegolf club head of claim 1, wherein the second material forming saidsecond face insert has a lower resiliency than the first materialforming said first face insert.
 3. The golf club head of claim 2,wherein said second material is an elastomer.
 4. The golf club head ofclaim 3, wherein said first material is a metal alloy.
 5. The golf clubhead of claim 1, wherein said cavity comprises a central region, a heelregion and a toe region, and wherein said first face insert is disposedin one of said heel and toe regions and said second face insert isdisposed in said central region.
 6. The golf club head of claim 5,wherein the second material forming said second face insert has a lowerresiliency than the first material forming said first face insert suchthat said front face proximal said central region will exhibit the sameeffective coefficient of restitution as said front face proximal saidone of said heel and toe regions.
 7. The golf club head of claim 1,wherein said cavity comprises a central region, a heel region and a toeregion, and wherein said first insert is disposed in said heel region ofsaid cavity and said second face insert is disposed in said centralregion of said cavity.
 8. The golf club head of claim 7, furthercomprising a fourth face insert disposed in said toe region of saidcavity and formed of the first material.
 9. The golf club head of claim8, wherein the second material forming said second face insert has alower resiliency than the first material forming said first face insertand said fourth face insert, such that said front face proximal saidcentral region will exhibit the same effective coefficient ofrestitution as said front face proximal said heel region and said toeregion.
 10. A golf club head comprising: a body having a rear surface, afront face, a heel end, a toe end and a cavity extending from the frontface toward the rear surface, said cavity having a central region and abottom surface; a face insert having a front surface and a back surface,said front surface including a striking surface on the front face ofsaid body; and a substrate disposed in said cavity sandwiched betweenthe back surface of said face insert and the bottom surface of saidcavity, said substrate having a resiliency that varies from a highresiliency value proximal the toe end of said body to a low resiliencyvalue proximal the central region of said cavity such that said golfclub head exhibits a substantially uniform effective coefficient ofrestitution across the face insert when striking a golf ball.
 11. Thegolf club head of claim 10, wherein said face insert comprises aplurality of elongate rod elements each having a first end, a second endand a side surface, and said plurality of elongate rod elements arrangedin a parallel closely packed array such that the side surface of each ofsaid plurality of elongate rod elements is in contact with a sidesurface of an adjacent one of said plurality of elongate rod elements.12. The golf club head of claim 10, wherein said substrate comprises afirst insert and a second insert, said first insert being formed of afirst material having a first resiliency value, said second insert beingformed of a second material having a second resiliency value less thansaid first resiliency value, and said second insert being locatedproximal the central region of said cavity.
 13. The golf club head ofclaim 11, wherein said substrate comprises a first insert and a secondinsert, said first insert being formed of a first material having afirst resiliency value, said second insert being formed of a secondmaterial having a second resiliency value less than said firstresiliency value, and said second insert being located proximal thecentral region of said cavity.
 14. The golf club head of claim 13,wherein said first material is a metal alloy and said second material isan elastomer.
 15. The golf club head of claim 10, wherein said substratealso has said high resiliency value proximal the heel end of said body.